/* Based on src/http/ngx_http_parse.c from NGINX copyright Igor Sysoev
 *
 * Additional changes are licensed under the same terms as NGINX and
 * copyright Joyent, Inc. and other Node contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */
#include "evpp/evpphttp/http_parser.h"

#include <assert.h>
#include <stddef.h>
#include <limits.h>
#include <stdlib.h>

#if __cplusplus
#include <limits>

namespace evpp {

#ifndef INT64_MAX
# define INT64_MAX std::numeric_limits<int64_t>::max()
#endif

#else
#define nullptr NULL

#endif /* __cplusplus */

#ifndef MIN
# define MIN(a,b) ((a) < (b) ? (a) : (b))
#endif


#if HTTP_PARSER_DEBUG
#define SET_ERRNO(e)                                                 \
do {                                                                 \
  parser->http_errno = (e);                                          \
  parser->error_lineno = __LINE__;                                   \
} while (0)
#else
#define SET_ERRNO(e)                                                 \
do {                                                                 \
  parser->http_errno = (e);                                          \
} while(0)
#endif

#define RETURN(r)                                                    \
do {                                                                 \
  parser->state = state;                                             \
  return (r);                                                        \
} while(0)

/* Run the notify callback FOR, returning ER if it fails */
#define _CALLBACK_NOTIFY(FOR, ER)                                    \
do {                                                                 \
  parser->state = state;                                             \
  assert(HTTP_PARSER_ERRNO(parser) == HPE_OK);                       \
                                                                     \
  if (0 != settings->on_##FOR(parser)) {                             \
    SET_ERRNO(HPE_CB_##FOR);                                         \
  }                                                                  \
                                                                     \
  /* We either errored above or got paused; get out */               \
  if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {                         \
    return (ER);                                                     \
  }                                                                  \
} while (0)

/* Run the notify callback FOR and consume the current byte */
#define CALLBACK_NOTIFY(FOR)            _CALLBACK_NOTIFY(FOR, p - data + 1)

/* Run the notify callback FOR and don't consume the current byte */
#define CALLBACK_NOTIFY_NOADVANCE(FOR)  _CALLBACK_NOTIFY(FOR, p - data)

/* Run data callback FOR with LEN bytes, returning ER if it fails */
#define _CALLBACK_DATA(FOR, LEN, ER)                                 \
do {                                                                 \
  parser->state = state;                                             \
  assert(HTTP_PARSER_ERRNO(parser) == HPE_OK);                       \
                                                                     \
  if (FOR##_mark) {                                                  \
    if (0 != settings->on_##FOR(parser, FOR##_mark, (LEN))) {        \
      SET_ERRNO(HPE_CB_##FOR);                                       \
    }                                                                \
                                                                     \
    /* We either errored above or got paused; get out */             \
    if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {                       \
      return (ER);                                                   \
    }                                                                \
    FOR##_mark = nullptr;                                               \
  }                                                                  \
} while (0)

/* Run the data callback FOR and consume the current byte */
#define CALLBACK_DATA(FOR)                                           \
    _CALLBACK_DATA(FOR, p - FOR##_mark, p - data + 1)

/* Run the data callback FOR and don't consume the current byte */
#define CALLBACK_DATA_NOADVANCE(FOR)                                 \
    _CALLBACK_DATA(FOR, p - FOR##_mark, p - data)

/* We just saw a synthetic space */
#define CALLBACK_SPACE(FOR)                                          \
do {                                                                 \
  parser->state = state;                                             \
  if (0 != settings->on_##FOR(parser, SPACE, 1)) {                   \
    SET_ERRNO(HPE_CB_##FOR);                                         \
    return (p - data);                                               \
  }                                                                  \
                                                                     \
  /* We either errored above or got paused; get out */               \
  if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {                         \
    return (p - data);                                               \
  }                                                                  \
} while (0)

/* Set the mark FOR; non-destructive if mark is already set */
#define MARK(FOR)                                                    \
do {                                                                 \
  if (!FOR##_mark) {                                                 \
    FOR##_mark = p;                                                  \
  }                                                                  \
} while (0)


#define CONTENT_LENGTH "content-length"
#define TRANSFER_ENCODING "transfer-encoding"
#define UPGRADE "upgrade"
#define CHUNKED "chunked"
#define SPACE " "


static const char *method_strings[] =
{   "DELETE"
    , "GET"
    , "HEAD"
    , "POST"
    , "PUT"
    , "CONNECT"
    , "OPTIONS"
    , "TRACE"
    , "COPY"
    , "LOCK"
    , "MKCOL"
    , "MOVE"
    , "PROPFIND"
    , "PROPPATCH"
    , "UNLOCK"
    , "REPORT"
    , "MKACTIVITY"
    , "CHECKOUT"
    , "MERGE"
    , "M-SEARCH"
    , "NOTIFY"
    , "SUBSCRIBE"
    , "UNSUBSCRIBE"
    , "PATCH"
};


/* Tokens as defined by rfc 2616. Also lowercases them.
 *        token       = 1*<any CHAR except CTLs or separators>
 *     separators     = "(" | ")" | "<" | ">" | "@"
 *                    | "," | ";" | ":" | "\" | <">
 *                    | "/" | "[" | "]" | "?" | "="
 *                    | "{" | "}" | SP | HT
 */
static const char tokens[256] = {
    /*   0 nul    1 soh    2 stx    3 etx    4 eot    5 enq    6 ack    7 bel  */
    0,       0,       0,       0,       0,       0,       0,       0,
    /*   8 bs     9 ht    10 nl    11 vt    12 np    13 cr    14 so    15 si   */
    0,       0,       0,       0,       0,       0,       0,       0,
    /*  16 dle   17 dc1   18 dc2   19 dc3   20 dc4   21 nak   22 syn   23 etb */
    0,       0,       0,       0,       0,       0,       0,       0,
    /*  24 can   25 em    26 sub   27 esc   28 fs    29 gs    30 rs    31 us  */
    0,       0,       0,       0,       0,       0,       0,       0,
    /*  32 sp    33  !    34  "    35  #    36  $    37  %    38  &    39  '  */
    0,      '!',      0,     '#',     '$',     '%',     '&',    '\'',
    /*  40  (    41  )    42  *    43  +    44  ,    45  -    46  .    47  /  */
    0,       0,      '*',     '+',      0,      '-',     '.',      0,
    /*  48  0    49  1    50  2    51  3    52  4    53  5    54  6    55  7  */
    '0',     '1',     '2',     '3',     '4',     '5',     '6',     '7',
    /*  56  8    57  9    58  :    59  ;    60  <    61  =    62  >    63  ?  */
    '8',     '9',      0,       0,       0,       0,       0,       0,
    /*  64  @    65  A    66  B    67  C    68  D    69  E    70  F    71  G  */
    0,      'a',     'b',     'c',     'd',     'e',     'f',     'g',
    /*  72  H    73  I    74  J    75  K    76  L    77  M    78  N    79  O  */
    'h',     'i',     'j',     'k',     'l',     'm',     'n',     'o',
    /*  80  P    81  Q    82  R    83  S    84  T    85  U    86  V    87  W  */
    'p',     'q',     'r',     's',     't',     'u',     'v',     'w',
    /*  88  X    89  Y    90  Z    91  [    92  \    93  ]    94  ^    95  _  */
    'x',     'y',     'z',      0,       0,       0,      '^',     '_',
    /*  96  `    97  a    98  b    99  c   100  d   101  e   102  f   103  g  */
    '`',     'a',     'b',     'c',     'd',     'e',     'f',     'g',
    /* 104  h   105  i   106  j   107  k   108  l   109  m   110  n   111  o  */
    'h',     'i',     'j',     'k',     'l',     'm',     'n',     'o',
    /* 112  p   113  q   114  r   115  s   116  t   117  u   118  v   119  w  */
    'p',     'q',     'r',     's',     't',     'u',     'v',     'w',
    /* 120  x   121  y   122  z   123  {   124  |   125  }   126  ~   127 del */
    'x',     'y',     'z',      0,      '|',      0,     '~',       0
};


static const int8_t unhex[256] =
{   -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
    ,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
    ,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
    , 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,-1,-1,-1,-1,-1,-1
    ,-1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1
    ,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
    ,-1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1
    ,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
};

#if HTTP_PARSER_STRICT
# define T(v) 0
#else
# define T(v) v
#endif

static const uint8_t normal_url_char[256] = {
    /*   0 nul    1 soh    2 stx    3 etx    4 eot    5 enq    6 ack    7 bel  */
    0,       0,       0,       0,       0,       0,       0,       0,
    /*   8 bs     9 ht    10 nl    11 vt    12 np    13 cr    14 so    15 si   */
    0,     T(1),      0,       0,     T(1),      0,       0,       0,
    /*  16 dle   17 dc1   18 dc2   19 dc3   20 dc4   21 nak   22 syn   23 etb */
    0,       0,       0,       0,       0,       0,       0,       0,
    /*  24 can   25 em    26 sub   27 esc   28 fs    29 gs    30 rs    31 us  */
    0,       0,       0,       0,       0,       0,       0,       0,
    /*  32 sp    33  !    34  "    35  #    36  $    37  %    38  &    39  '  */
    0,       1,       1,       0,       1,       1,       1,       1,
    /*  40  (    41  )    42  *    43  +    44  ,    45  -    46  .    47  /  */
    1,       1,       1,       1,       1,       1,       1,       1,
    /*  48  0    49  1    50  2    51  3    52  4    53  5    54  6    55  7  */
    1,       1,       1,       1,       1,       1,       1,       1,
    /*  56  8    57  9    58  :    59  ;    60  <    61  =    62  >    63  ?  */
    1,       1,       1,       1,       1,       1,       1,       0,
    /*  64  @    65  A    66  B    67  C    68  D    69  E    70  F    71  G  */
    1,       1,       1,       1,       1,       1,       1,       1,
    /*  72  H    73  I    74  J    75  K    76  L    77  M    78  N    79  O  */
    1,       1,       1,       1,       1,       1,       1,       1,
    /*  80  P    81  Q    82  R    83  S    84  T    85  U    86  V    87  W  */
    1,       1,       1,       1,       1,       1,       1,       1,
    /*  88  X    89  Y    90  Z    91  [    92  \    93  ]    94  ^    95  _  */
    1,       1,       1,       1,       1,       1,       1,       1,
    /*  96  `    97  a    98  b    99  c   100  d   101  e   102  f   103  g  */
    1,       1,       1,       1,       1,       1,       1,       1,
    /* 104  h   105  i   106  j   107  k   108  l   109  m   110  n   111  o  */
    1,       1,       1,       1,       1,       1,       1,       1,
    /* 112  p   113  q   114  r   115  s   116  t   117  u   118  v   119  w  */
    1,       1,       1,       1,       1,       1,       1,       1,
    /* 120  x   121  y   122  z   123  {   124  |   125  }   126  ~   127 del */
    1,       1,       1,       1,       1,       1,       1,       0,
};

#undef T

enum state
{   s_dead = 1 /* important that this is > 0 */
    , s_pre_start_req_or_res
    , s_start_req_or_res
    , s_res_or_resp_H

    , s_pre_start_res
    , s_start_res
    , s_res_H
    , s_res_HT
    , s_res_HTT
    , s_res_HTTP
    , s_res_first_http_major
    , s_res_http_major
    , s_res_first_http_minor
    , s_res_http_minor
    , s_res_first_status_code
    , s_res_status_code
    , s_res_status_start
    , s_res_status
    , s_res_line_almost_done

    , s_pre_start_req
    , s_start_req
    , s_req_method
    , s_req_spaces_before_url
    , s_req_schema
    , s_req_schema_slash
    , s_req_schema_slash_slash
    , s_req_server_start
    , s_req_server
    , s_req_server_with_at
    , s_req_host_start
    , s_req_host
    , s_req_host_ipv6
    , s_req_host_done
    , s_req_port
    , s_req_path
    , s_req_query_string_start
    , s_req_query_string
    , s_req_fragment_start
    , s_req_fragment
    , s_req_http_start
    , s_req_http_H
    , s_req_http_HT
    , s_req_http_HTT
    , s_req_http_HTTP
    , s_req_first_http_major
    , s_req_http_major
    , s_req_first_http_minor
    , s_req_http_minor
    , s_req_line_almost_done

    , s_header_field_start
    , s_header_field
    , s_header_value_start
    , s_header_value
    , s_header_value_lws

    , s_header_almost_done

    , s_chunk_size_start
    , s_chunk_size
    , s_chunk_parameters
    , s_chunk_size_almost_done

    , s_headers_almost_done
    , s_headers_done

    /* Important: 's_headers_done' must be the last 'header' state. All
     * states beyond this must be 'body' states. It is used for overflow
     * checking. See the PARSING_HEADER() macro.
     */

    , s_chunk_data
    , s_chunk_data_almost_done
    , s_chunk_data_done

    , s_body_identity
    , s_body_identity_eof

    , s_message_done
};


#define PARSING_HEADER(state) (state <= s_headers_done)


enum header_states
{   h_general = 0

    , h_general_and_quote
    , h_general_and_quote_and_escape

    , h_matching_content_length
    , h_matching_transfer_encoding
    , h_matching_upgrade

    , h_content_length
    , h_transfer_encoding
    , h_upgrade

    , h_matching_transfer_encoding_chunked

    , h_transfer_encoding_chunked
};

enum http_host_state
{
    s_http_host_dead = 1
    , s_http_userinfo_start
    , s_http_userinfo
    , s_http_host_start
    , s_http_host_v6_start
    , s_http_host
    , s_http_host_v6
    , s_http_host_v6_end
    , s_http_host_port_start
    , s_http_host_port
};


/* Macros for character classes; depends on strict-mode  */
#define CR                  '\r'
#define LF                  '\n'
#define QT                  '"'
#define BS                  '\\'
#define LOWER(c)            (unsigned char)(c | 0x20)
#define TOKEN(c)            (tokens[(unsigned char)c])
#define IS_ALPHA(c)         (LOWER(c) >= 'a' && LOWER(c) <= 'z')
#define IS_NUM(c)           ((c) >= '0' && (c) <= '9')
#define IS_ALPHANUM(c)      (IS_ALPHA(c) || IS_NUM(c))
#define IS_HEX(c)           (IS_NUM(c) || (LOWER(c) >= 'a' && LOWER(c) <= 'f'))
#define IS_MARK(c)          ((c) == '-' || (c) == '_' || (c) == '.' || \
  (c) == '!' || (c) == '~' || (c) == '*' || (c) == '\'' || (c) == '(' || \
  (c) == ')')
#define IS_USERINFO_CHAR(c) (IS_ALPHANUM(c) || IS_MARK(c) || (c) == '%' || \
  (c) == ';' || (c) == ':' || (c) == '&' || (c) == '=' || (c) == '+' || \
  (c) == '$' || (c) == ',')

#if HTTP_PARSER_STRICT
#define IS_URL_CHAR(c)      (normal_url_char[(unsigned char) (c)])
#define IS_HOST_CHAR(c)     (IS_ALPHANUM(c) || (c) == '.' || (c) == '-')
#else
#define IS_URL_CHAR(c)                                                         \
  (normal_url_char[(unsigned char) (c)] || ((c) & 0x80))
#define IS_HOST_CHAR(c)                                                        \
  (IS_ALPHANUM(c) || (c) == '.' || (c) == '-' || (c) == '_')
#endif

/**
 * Verify that a char is a valid visible (printable) US-ASCII
 * character or %x80-FF
 **/
#define IS_HEADER_CHAR(ch)                                                     \
  (ch == CR || ch == LF || ch == 9 || ((unsigned char)ch > 31 && ch != 127))

#define start_state (parser->type == HTTP_REQUEST ? s_pre_start_req : s_pre_start_res)

#define STRICT_CHECK(cond)
#define NEW_MESSAGE() start_state

/* Map errno values to strings for human-readable output */
#define HTTP_STRERROR_GEN(n, s) { "HPE_" #n, s },
static struct {
    const char *name;
    const char *description;
} http_strerror_tab[] = {
    HTTP_ERRNO_MAP(HTTP_STRERROR_GEN)
};
#undef HTTP_STRERROR_GEN

/* Our URL parser.
 *
 * This is designed to be shared by http_parser_execute() for URL validation,
 * hence it has a state transition + byte-for-byte interface. In addition, it
 * is meant to be embedded in http_parser_parse_url(), which does the dirty
 * work of turning state transitions URL components for its API.
 *
 * This function should only be invoked with non-space characters. It is
 * assumed that the caller cares about (and can detect) the transition between
 * URL and non-URL states by looking for these.
 */
static enum state
parse_url_char(enum state s, const char ch)
{
    if (ch == ' ' || ch == '\r' || ch == '\n') {
        return s_dead;
    }

#if HTTP_PARSER_STRICT
    if (ch == '\t' || ch == '\f') {
        return s_dead;
    }
#endif

    switch (s) {
    case s_req_spaces_before_url:
        /* Proxied requests are followed by scheme of an absolute URI (alpha).
         * All methods except CONNECT are followed by '/' or '*'.
         */

        if (ch == '/' || ch == '*') {
            return s_req_path;
        }

        if (IS_ALPHA(ch)) {
            return s_req_schema;
        }

        break;

    case s_req_schema:
        if (IS_ALPHA(ch)) {
            return s;
        }

        if (ch == ':') {
            return s_req_schema_slash;
        }

        break;

    case s_req_schema_slash:
        if (ch == '/') {
            return s_req_schema_slash_slash;
        }

        break;

    case s_req_schema_slash_slash:
        if (ch == '/') {
            return s_req_server_start;
        }

        break;

    case s_req_server_with_at:
        if (ch == '@') {
            return s_dead;
        }

    /* FALLTHROUGH */
    case s_req_server_start:
    case s_req_server:
        if (ch == '/') {
            return s_req_path;
        }

        if (ch == '?') {
            return s_req_query_string_start;
        }

        if (ch == '@') {
            return s_req_server_with_at;
        }

        if (IS_USERINFO_CHAR(ch) || ch == '[' || ch == ']') {
            return s_req_server;
        }

        break;

    case s_req_path:
        if (IS_URL_CHAR(ch)) {
            return s;
        }

        switch (ch) {
        case '?':
            return s_req_query_string_start;

        case '#':
            return s_req_fragment_start;
        }

        break;

    case s_req_query_string_start:
    case s_req_query_string:
        if (IS_URL_CHAR(ch)) {
            return s_req_query_string;
        }

        switch (ch) {
        case '?':
            /* allow extra '?' in query string */
            return s_req_query_string;

        case '#':
            return s_req_fragment_start;
        }

        break;

    case s_req_fragment_start:
        if (IS_URL_CHAR(ch)) {
            return s_req_fragment;
        }

        switch (ch) {
        case '?':
            return s_req_fragment;

        case '#':
            return s;
        }

        break;

    case s_req_fragment:
        if (IS_URL_CHAR(ch)) {
            return s;
        }

        switch (ch) {
        case '?':
        case '#':
            return s;
        }

        break;

    default:
        break;
    }

    /* We should never fall out of the switch above unless there's an error */
    return s_dead;
}

size_t http_parser_execute (http_parser *parser,
                            const http_parser_settings *settings,
                            const char *data,
                            size_t len)
{
    char c, ch;
    int8_t unhex_val;
    const char *p = data;

    /* Optimization: within the parsing loop below, we refer to this
     * local copy of the state rather than parser->state.  The compiler
     * can't be sure whether parser->state will change during a callback,
     * so it generates a lot of memory loads and stores to keep a register
     * copy of the state in sync with the memory copy.  We know, however,
     * that the callbacks aren't allowed to change the parser state, so
     * the parsing loop works with this local variable and only copies
     * the value back to parser->loop before returning or invoking a
     * callback.
     */
    unsigned char state = parser->state;
    const unsigned int lenient = 0;

    /* We're in an error state. Don't bother doing anything. */
    if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {
        RETURN(0);
    }

    if (len == 0) {
        switch (state) {
        case s_body_identity_eof:
            /* Use of CALLBACK_NOTIFY() here would erroneously return 1 byte read if
             * we got paused.
             */
            CALLBACK_NOTIFY_NOADVANCE(message_complete);
            RETURN(0);

        case s_pre_start_req_or_res:
        case s_pre_start_res:
        case s_pre_start_req:
            RETURN(0);

        default:
            SET_ERRNO(HPE_INVALID_EOF_STATE);
            RETURN(1);
        }
    }

    /* technically we could combine all of these (except for url_mark) into one
       variable, saving stack space, but it seems more clear to have them
       separated. */
    const char *header_field_mark = 0;
    const char *header_value_mark = 0;
    const char *url_mark = 0;
    const char *reason_mark = 0;
    const char *body_mark = 0;

    if (state == s_header_field)
        header_field_mark = data;
    if (state == s_header_value)
        header_value_mark = data;
    if (state == s_req_path ||
            state == s_req_schema ||
            state == s_req_schema_slash ||
            state == s_req_schema_slash_slash ||
            state == s_req_port ||
            state == s_req_query_string_start ||
            state == s_req_query_string ||
            state == s_req_host_start ||
            state == s_req_host ||
            state == s_req_host_ipv6 ||
            state == s_req_host_done ||
            state == s_req_fragment_start ||
            state == s_req_fragment)
        url_mark = data;
    if (state == s_res_status)
        reason_mark = data;

    /* Used only for overflow checking. If the parser is in a parsing-headers
     * state, then its value is equal to max(data, the beginning of the current
     * message or chunk). If the parser is in a not-parsing-headers state, then
     * its value is irrelevant.
     */
    const char* data_or_header_data_start = data;

    for (p = data; p != data + len; p++) {
        ch = *p;

reexecute_byte:
        switch (state) {

        case s_pre_start_req_or_res:
            if (ch == CR || ch == LF)
                break;
            state = s_start_req_or_res;
            CALLBACK_NOTIFY_NOADVANCE(message_begin);
            goto reexecute_byte;

        case s_start_req_or_res:
        {
            parser->flags = 0;
            parser->content_length = -1;

            if (ch == 'H') {
                state = s_res_or_resp_H;
            } else {
                parser->type = HTTP_REQUEST;
                state = s_start_req;
                goto reexecute_byte;
            }

            break;
        }

        case s_res_or_resp_H:
            if (ch == 'T') {
                parser->type = HTTP_RESPONSE;
                state = s_res_HT;
            } else {
                if (ch != 'E') {
                    SET_ERRNO(HPE_INVALID_CONSTANT);
                    goto error;
                }

                parser->type = HTTP_REQUEST;
                parser->method = HTTP_HEAD;
                parser->index = 2;
                state = s_req_method;
            }
            break;

        case s_pre_start_res:
            if (ch == CR || ch == LF)
                break;
            state = s_start_res;
            CALLBACK_NOTIFY_NOADVANCE(message_begin);
            goto reexecute_byte;

        case s_start_res:
        {
            parser->flags = 0;
            parser->content_length = -1;

            switch (ch) {
            case 'H':
                state = s_res_H;
                break;

            default:
                SET_ERRNO(HPE_INVALID_CONSTANT);
                goto error;
            }

            break;
        }

        case s_res_H:
            STRICT_CHECK(ch != 'T');
            state = s_res_HT;
            break;

        case s_res_HT:
            STRICT_CHECK(ch != 'T');
            state = s_res_HTT;
            break;

        case s_res_HTT:
            STRICT_CHECK(ch != 'P');
            state = s_res_HTTP;
            break;

        case s_res_HTTP:
            STRICT_CHECK(ch != '/');
            state = s_res_first_http_major;
            break;

        case s_res_first_http_major:
            if (ch < '0' || ch > '9') {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_major = ch - '0';
            state = s_res_http_major;
            break;

        /* major HTTP version or dot */
        case s_res_http_major:
        {
            if (ch == '.') {
                state = s_res_first_http_minor;
                break;
            }

            if (!IS_NUM(ch)) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_major *= 10;
            parser->http_major += ch - '0';

            if (parser->http_major > 999) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            break;
        }

        /* first digit of minor HTTP version */
        case s_res_first_http_minor:
            if (!IS_NUM(ch)) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_minor = ch - '0';
            state = s_res_http_minor;
            break;

        /* minor HTTP version or end of request line */
        case s_res_http_minor:
        {
            if (ch == ' ') {
                state = s_res_first_status_code;
                break;
            }

            if (!IS_NUM(ch)) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_minor *= 10;
            parser->http_minor += ch - '0';

            if (parser->http_minor > 999) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            break;
        }

        case s_res_first_status_code:
        {
            if (!IS_NUM(ch)) {
                if (ch == ' ') {
                    break;
                }

                SET_ERRNO(HPE_INVALID_STATUS);
                goto error;
            }
            parser->status_code = ch - '0';
            state = s_res_status_code;
            break;
        }

        case s_res_status_code:
        {
            if (!IS_NUM(ch)) {
                switch (ch) {
                case ' ':
                    state = s_res_status;
                    break;
                case CR:
                    state = s_res_line_almost_done;
                    break;
                case LF:
                    state = s_header_field_start;
                    break;
                default:
                    SET_ERRNO(HPE_INVALID_STATUS);
                    goto error;
                }
                break;
            }

            parser->status_code *= 10;
            parser->status_code += ch - '0';

            if (parser->status_code > 999) {
                SET_ERRNO(HPE_INVALID_STATUS);
                goto error;
            }

            break;
        }

        case s_res_status:
            /* the human readable status. e.g. "NOT FOUND" */
            MARK(reason);
            if (ch == CR) {
                state = s_res_line_almost_done;
                CALLBACK_DATA(reason);
                break;
            }

            if (ch == LF) {
                state = s_header_field_start;
                CALLBACK_DATA(reason);
                break;
            }
            break;

        case s_res_line_almost_done:
            STRICT_CHECK(ch != LF);
            state = s_header_field_start;
            break;

        case s_pre_start_req:
            if (ch == CR || ch == LF) {
                break;
            }
            state = s_start_req;
            CALLBACK_NOTIFY_NOADVANCE(message_begin);
            goto reexecute_byte;

        case s_start_req:
        {
            parser->flags = 0;
            parser->content_length = -1;

            if (!IS_ALPHA(ch)) {
                SET_ERRNO(HPE_INVALID_METHOD);
                goto error;
            }

            parser->method = (enum http_method) 0;
            parser->index = 1;
            switch (ch) {
            case 'C':
                parser->method = HTTP_CONNECT; /* or COPY, CHECKOUT */ break;
            case 'D':
                parser->method = HTTP_DELETE;
                break;
            case 'G':
                parser->method = HTTP_GET;
                break;
            case 'H':
                parser->method = HTTP_HEAD;
                break;
            case 'L':
                parser->method = HTTP_LOCK;
                break;
            case 'M':
                parser->method = HTTP_MKCOL; /* or MOVE, MKACTIVITY, MERGE, M-SEARCH */ break;
            case 'N':
                parser->method = HTTP_NOTIFY;
                break;
            case 'O':
                parser->method = HTTP_OPTIONS;
                break;
            case 'P':
                parser->method = HTTP_POST;
                /* or PROPFIND or PROPPATCH or PUT or PATCH */
                break;
            case 'R':
                parser->method = HTTP_REPORT;
                break;
            case 'S':
                parser->method = HTTP_SUBSCRIBE;
                break;
            case 'T':
                parser->method = HTTP_TRACE;
                break;
            case 'U':
                parser->method = HTTP_UNLOCK; /* or UNSUBSCRIBE */ break;
            default:
                SET_ERRNO(HPE_INVALID_METHOD);
                goto error;
            }
            state = s_req_method;

            break;
        }

        case s_req_method:
        {
            if (ch == '\0') {
                SET_ERRNO(HPE_INVALID_METHOD);
                goto error;
            }

            const char *matcher = method_strings[parser->method];
            if (ch == ' ' && matcher[parser->index] == '\0') {
                state = s_req_spaces_before_url;
            } else if (ch == matcher[parser->index]) {
                ; /* nada */
            } else if (parser->method == HTTP_CONNECT) {
                if (parser->index == 1 && ch == 'H') {
                    parser->method = HTTP_CHECKOUT;
                } else if (parser->index == 2  && ch == 'P') {
                    parser->method = HTTP_COPY;
                } else {
                    goto error;
                }
            } else if (parser->method == HTTP_MKCOL) {
                if (parser->index == 1 && ch == 'O') {
                    parser->method = HTTP_MOVE;
                } else if (parser->index == 1 && ch == 'E') {
                    parser->method = HTTP_MERGE;
                } else if (parser->index == 1 && ch == '-') {
                    parser->method = HTTP_MSEARCH;
                } else if (parser->index == 2 && ch == 'A') {
                    parser->method = HTTP_MKACTIVITY;
                } else {
                    goto error;
                }
            } else if (parser->index == 1 && parser->method == HTTP_POST) {
                if (ch == 'R') {
                    parser->method = HTTP_PROPFIND; /* or HTTP_PROPPATCH */
                } else if (ch == 'U') {
                    parser->method = HTTP_PUT;
                } else if (ch == 'A') {
                    parser->method = HTTP_PATCH;
                } else {
                    goto error;
                }
            } else if (parser->index == 2 && parser->method == HTTP_UNLOCK && ch == 'S') {
                parser->method = HTTP_UNSUBSCRIBE;
            } else if (parser->index == 4 && parser->method == HTTP_PROPFIND && ch == 'P') {
                parser->method = HTTP_PROPPATCH;
            } else {
                SET_ERRNO(HPE_INVALID_METHOD);
                goto error;
            }

            ++parser->index;
            break;
        }

        case s_req_spaces_before_url:
        {
            if (ch == ' ') break;

            // CONNECT requests must be followed by a <host>:<port>
            if (parser->method == HTTP_CONNECT) {
                MARK(url);
                state = s_req_host_start;
                goto reexecute_byte;
            }

            if (ch == '/' || ch == '*') {
                MARK(url);
                state = s_req_path;
                break;
            }

            /* Proxied requests are followed by scheme of an absolute URI (alpha).
             * All other methods are followed by '/' or '*' (handled above).
             */
            if (IS_ALPHA(ch)) {
                MARK(url);
                state = s_req_schema;
                break;
            }

            SET_ERRNO(HPE_INVALID_URL);
            goto error;
        }

        case s_req_schema:
        {
            if (IS_ALPHA(ch)) break;

            if (ch == ':') {
                state = s_req_schema_slash;
                break;
            }

            SET_ERRNO(HPE_INVALID_URL);
            goto error;
        }

        case s_req_schema_slash:
            STRICT_CHECK(ch != '/');
            state = s_req_schema_slash_slash;
            break;

        case s_req_schema_slash_slash:
            STRICT_CHECK(ch != '/');
            state = s_req_host_start;
            break;

        case s_req_host_start:
            if (ch == '[') {
                state = s_req_host_ipv6;
                break;
            } else if (IS_ALPHANUM(ch)) {
                state = s_req_host;
                break;
            }

            SET_ERRNO(HPE_INVALID_HOST);
            goto error;

        case s_req_host:
            if (IS_HOST_CHAR(ch)) break;
            state = s_req_host_done;
            goto reexecute_byte;

        case s_req_host_ipv6:
            if (IS_HEX(ch) || ch == ':') break;
            if (ch == ']') {
                state = s_req_host_done;
                break;
            }

            SET_ERRNO(HPE_INVALID_HOST);
            goto error;

        case s_req_host_done:
            switch (ch) {
            case ':':
                state = s_req_port;
                break;
            case '/':
                state = s_req_path;
                break;
            case ' ':
                /* The request line looks like:
                 *   "GET http://foo.bar.com HTTP/1.1"
                 * That is, there is no path.
                 */
                state = s_req_http_start;
                CALLBACK_DATA(url);
                break;
            case '?':
                state = s_req_query_string_start;
                break;
            default:
                SET_ERRNO(HPE_INVALID_HOST);
                goto error;
            }

            break;

        case s_req_port:
        {
            if (IS_NUM(ch)) break;
            switch (ch) {
            case '/':
                state = s_req_path;
                break;
            case ' ':
                /* The request line looks like:
                 *   "GET http://foo.bar.com:1234 HTTP/1.1"
                 * That is, there is no path.
                 */
                state = s_req_http_start;
                CALLBACK_DATA(url);
                break;
            case '?':
                state = s_req_query_string_start;
                break;
            default:
                SET_ERRNO(HPE_INVALID_PORT);
                goto error;
            }
            break;
        }

        case s_req_path:
        {
            if (IS_URL_CHAR(ch)) break;

            switch (ch) {
            case ' ':
                state = s_req_http_start;
                CALLBACK_DATA(url);
                break;
            case CR:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_req_line_almost_done;
                CALLBACK_DATA(url);
                break;
            case LF:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_header_field_start;
                CALLBACK_DATA(url);
                break;
            case '?':
                state = s_req_query_string_start;
                break;
            case '#':
                state = s_req_fragment_start;
                break;
            default:
                SET_ERRNO(HPE_INVALID_PATH);
                goto error;
            }
            break;
        }

        case s_req_query_string_start:
        {
            if (IS_URL_CHAR(ch)) {
                state = s_req_query_string;
                break;
            }

            switch (ch) {
            case '?':
                break; /* XXX ignore extra '?' ... is this right? */
            case ' ':
                state = s_req_http_start;
                CALLBACK_DATA(url);
                break;
            case CR:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_req_line_almost_done;
                CALLBACK_DATA(url);
                break;
            case LF:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_header_field_start;
                CALLBACK_DATA(url);
                break;
            case '#':
                state = s_req_fragment_start;
                break;
            default:
                SET_ERRNO(HPE_INVALID_QUERY_STRING);
                goto error;
            }
            break;
        }

        case s_req_query_string:
        {
            if (IS_URL_CHAR(ch)) break;

            switch (ch) {
            case '?':
                /* allow extra '?' in query string */
                break;
            case ' ':
                state = s_req_http_start;
                CALLBACK_DATA(url);
                break;
            case CR:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_req_line_almost_done;
                CALLBACK_DATA(url);
                break;
            case LF:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_header_field_start;
                CALLBACK_DATA(url);
                break;
            case '#':
                state = s_req_fragment_start;
                break;
            default:
                SET_ERRNO(HPE_INVALID_QUERY_STRING);
                goto error;
            }
            break;
        }

        case s_req_fragment_start:
        {
            if (IS_URL_CHAR(ch)) {
                state = s_req_fragment;
                break;
            }

            switch (ch) {
            case ' ':
                state = s_req_http_start;
                CALLBACK_DATA(url);
                break;
            case CR:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_req_line_almost_done;
                CALLBACK_DATA(url);
                break;
            case LF:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_header_field_start;
                CALLBACK_DATA(url);
                break;
            case '?':
                state = s_req_fragment;
                break;
            case '#':
                break;
            default:
                SET_ERRNO(HPE_INVALID_FRAGMENT);
                goto error;
            }
            break;
        }

        case s_req_fragment:
        {
            if (IS_URL_CHAR(ch)) break;

            switch (ch) {
            case ' ':
                state = s_req_http_start;
                CALLBACK_DATA(url);
                break;
            case CR:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_req_line_almost_done;
                CALLBACK_DATA(url);
                break;
            case LF:
                parser->http_major = 0;
                parser->http_minor = 9;
                state = s_header_field_start;
                CALLBACK_DATA(url);
                break;
            case '?':
            case '#':
                break;
            default:
                SET_ERRNO(HPE_INVALID_FRAGMENT);
                goto error;
            }
            break;
        }

        case s_req_http_start:
            switch (ch) {
            case 'H':
                state = s_req_http_H;
                break;
            case ' ':
                break;
            default:
                SET_ERRNO(HPE_INVALID_CONSTANT);
                goto error;
            }
            break;

        case s_req_http_H:
            STRICT_CHECK(ch != 'T');
            state = s_req_http_HT;
            break;

        case s_req_http_HT:
            STRICT_CHECK(ch != 'T');
            state = s_req_http_HTT;
            break;

        case s_req_http_HTT:
            STRICT_CHECK(ch != 'P');
            state = s_req_http_HTTP;
            break;

        case s_req_http_HTTP:
            STRICT_CHECK(ch != '/');
            state = s_req_first_http_major;
            break;

        /* first digit of major HTTP version */
        case s_req_first_http_major:
            if (ch < '0' || ch > '9') {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_major = ch - '0';
            state = s_req_http_major;
            break;

        /* major HTTP version or dot */
        case s_req_http_major:
        {
            if (ch == '.') {
                state = s_req_first_http_minor;
                break;
            }

            if (!IS_NUM(ch)) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_major *= 10;
            parser->http_major += ch - '0';

            if (parser->http_major > 999) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            break;
        }

        /* first digit of minor HTTP version */
        case s_req_first_http_minor:
            if (!IS_NUM(ch)) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_minor = ch - '0';
            state = s_req_http_minor;
            break;

        /* minor HTTP version or end of request line */
        case s_req_http_minor:
        {
            if (ch == CR) {
                state = s_req_line_almost_done;
                break;
            }

            if (ch == LF) {
                state = s_header_field_start;
                break;
            }

            /* XXX allow spaces after digit? */

            if (!IS_NUM(ch)) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            parser->http_minor *= 10;
            parser->http_minor += ch - '0';

            if (parser->http_minor > 999) {
                SET_ERRNO(HPE_INVALID_VERSION);
                goto error;
            }

            break;
        }

        /* end of request line */
        case s_req_line_almost_done:
        {
            if (ch != LF) {
                SET_ERRNO(HPE_LF_EXPECTED);
                goto error;
            }

            state = s_header_field_start;
            break;
        }

        case s_header_field_start:
        {
            if (ch == CR) {
                state = s_headers_almost_done;
                break;
            }

            if (ch == LF) {
                /* they might be just sending \n instead of \r\n so this would be
                 * the second \n to denote the end of headers*/
                state = s_headers_almost_done;
                goto reexecute_byte;
            }

            c = TOKEN(ch);

            if (!c) {
                SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
                goto error;
            }

            MARK(header_field);

            parser->index = 0;
            state = s_header_field;

            switch (c) {
            case 'c':
                parser->header_state = h_matching_content_length;
                break;

            case 't':
                parser->header_state = h_matching_transfer_encoding;
                break;

            case 'u':
                parser->header_state = h_matching_upgrade;
                break;

            default:
                parser->header_state = h_general;
                break;
            }
            break;
        }

        case s_header_field:
        {
            c = TOKEN(ch);

            if (c) {
                switch (parser->header_state) {
                case h_general:

                    // fast-forwarding, wheeeeeee!
#define MOVE_THE_HEAD do { \
++p;                     \
if (!TOKEN(*p)) {        \
  ch = *p;               \
  goto notatoken;        \
}                        \
  } while(0);

                    if (data + len - p >= 9) {
                        MOVE_THE_HEAD
                        MOVE_THE_HEAD
                        MOVE_THE_HEAD
                        MOVE_THE_HEAD
                        MOVE_THE_HEAD
                        MOVE_THE_HEAD
                        MOVE_THE_HEAD
                        MOVE_THE_HEAD
                    } else if (data + len - p >= 4) {
                        MOVE_THE_HEAD
                        MOVE_THE_HEAD
                        MOVE_THE_HEAD
                    }

                    break;

                /* content-length */

                case h_matching_content_length:
                    parser->index++;
                    if (parser->index > sizeof(CONTENT_LENGTH)-1
                            || c != CONTENT_LENGTH[parser->index]) {
                        parser->header_state = h_general;
                    } else if (parser->index == sizeof(CONTENT_LENGTH)-2) {
                        parser->header_state = h_content_length;
                    }
                    break;

                /* transfer-encoding */

                case h_matching_transfer_encoding:
                    parser->index++;
                    if (parser->index > sizeof(TRANSFER_ENCODING)-1
                            || c != TRANSFER_ENCODING[parser->index]) {
                        parser->header_state = h_general;
                    } else if (parser->index == sizeof(TRANSFER_ENCODING)-2) {
                        parser->header_state = h_transfer_encoding;
                    }
                    break;

                /* upgrade */

                case h_matching_upgrade:
                    parser->index++;
                    if (parser->index > sizeof(UPGRADE)-1
                            || c != UPGRADE[parser->index]) {
                        parser->header_state = h_general;
                    } else if (parser->index == sizeof(UPGRADE)-2) {
                        parser->header_state = h_upgrade;
                    }
                    break;

                case h_content_length:
                case h_transfer_encoding:
                case h_upgrade:
                    if (ch != ' ') parser->header_state = h_general;
                    break;

                default:
                    assert(0 && "Unknown header_state");
                    break;
                }
                break;
            }

notatoken:
            if (ch == ':') {
                state = s_header_value_start;
                // do not allow headers with trailing whitespaces
                // https://tools.ietf.org/html/rfc7230#section-3.2.4
                if (p - header_field_mark > 1 &&
                        data[p - data - 1] == ' ') {
                    SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
                    goto error;
                }
                CALLBACK_DATA(header_field);
                break;
            }

            SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
            goto error;
        }

        case s_header_value_start:
        {
            if (ch == ' ' || ch == '\t') break;

            MARK(header_value);

            state = s_header_value;
            parser->index = 0;

            // Error out if a content_length, transfer_encoding, or upgrade header
            // was present with no actual value.  These headers correspond with
            // special parser states that without the below accept empty header
            // values and so we can reject such requests here in the parser.
            // If more headers are added, can consider moving to a hash/map based
            // model below.
            if (ch == CR || ch == LF) {
                if (parser->header_state == h_content_length) {
                    SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                } else if (parser->header_state == h_transfer_encoding) {
                    SET_ERRNO(HPE_INVALID_TRANSFER_ENCODING);
                } else if (parser->header_state == h_upgrade) {
                    SET_ERRNO(HPE_INVALID_UPGRADE);
                }

                if (parser->http_errno != HPE_OK) {
                    goto error;
                }
            }

            if (ch == CR) {
                STRICT_CHECK(parser->quote != 0);
                parser->header_state = h_general;
                state = s_header_almost_done;
                CALLBACK_DATA(header_value);
                break;
            }

            if (ch == LF) {
                STRICT_CHECK(parser->quote != 0);
                state = s_header_field_start;
                CALLBACK_DATA(header_value);
                break;
            }

            c = LOWER(ch);

            switch (parser->header_state) {
            case h_upgrade:
                parser->flags |= F_UPGRADE;
                parser->header_state = h_general;
                break;

            case h_transfer_encoding:
                /* looking for 'Transfer-Encoding: chunked' */
                if ('c' == c) {
                    parser->header_state = h_matching_transfer_encoding_chunked;
                } else {
                    parser->header_state = h_general;
                }
                break;

            case h_content_length:
                if (!IS_NUM(ch)) {
                    SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                    goto error;
                }

                parser->content_length = ch - '0';
                break;

            default:
                parser->header_state = ch == QT ? h_general_and_quote : h_general;
                break;
            }
            break;
        }

        case s_header_value:
        {
cr_or_lf_or_qt:
            if (ch == CR &&
                    parser->header_state != h_general_and_quote_and_escape) {
                state = s_header_almost_done;
                CALLBACK_DATA(header_value);
                break;
            }

            if (ch == LF &&
                    parser->header_state != h_general_and_quote_and_escape) {
                state = s_header_almost_done;
                CALLBACK_DATA_NOADVANCE(header_value);
                goto reexecute_byte;
            }

            if (!lenient && !IS_HEADER_CHAR(ch) &&
                    parser->header_state != h_general_and_quote_and_escape) {
                SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
                goto error;
            }

            switch (parser->header_state) {
            case h_general:
                if (ch == QT) {
                    parser->header_state = h_general_and_quote;
                }

                // fast-forwarding, wheee!
#define MOVE_FAST do {                    \
  ++p;                                    \
  ch = *p;                                \
  if (ch == CR || ch == LF || ch == QT || \
  ch == BS || !IS_HEADER_CHAR(ch)) {  \
goto cr_or_lf_or_qt;                  \
  }                                       \
} while(0);

                if (data + len - p >= 12) {
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                } else if (data + len - p >= 5) {
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                    MOVE_FAST
                }

                break;

            case h_general_and_quote:
                if (ch == QT) {
                    parser->header_state = h_general;
                } else if (ch == BS) {
                    parser->header_state = h_general_and_quote_and_escape;
                }
                break;

            case h_general_and_quote_and_escape:
                parser->header_state = h_general_and_quote;
                break;

            // Not sure the below is relevant anymore as from
            // s_header_value_start it appears as though we can never
            // be in the situation below
            case h_transfer_encoding:
                SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
                goto error;
                break;

            case h_content_length:
                if (ch == ' ') break;
                if (!IS_NUM(ch)) {
                    SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                    goto error;
                }

                if (parser->content_length > ((INT64_MAX - 10) / 10)) {
                    /* overflow */
                    SET_ERRNO(HPE_HUGE_CONTENT_LENGTH);
                    goto error;
                }

                parser->content_length *= 10;
                parser->content_length += ch - '0';
                break;

            /* Transfer-Encoding: chunked */
            case h_matching_transfer_encoding_chunked:
                parser->index++;
                if (parser->index > sizeof(CHUNKED)-1
                        || LOWER(ch) != CHUNKED[parser->index]) {
                    parser->header_state = h_general;
                } else if (parser->index == sizeof(CHUNKED)-2) {
                    parser->header_state = h_transfer_encoding_chunked;
                }
                break;

            case h_transfer_encoding_chunked:
                if (ch != ' ') {
                    parser->header_state = h_general;
                }
                break;

            default:
                state = s_header_value;
                parser->header_state = h_general;
                break;
            }
            break;
        }

        case s_header_almost_done:
        {
            if (ch == LF) {
                state = s_header_value_lws;
            } else {
                state = s_header_value;
            }

            switch (parser->header_state) {
            case h_transfer_encoding_chunked:
                parser->flags |= F_CHUNKED;
                break;
            default:
                break;
            }

            if (ch != LF) {
                CALLBACK_SPACE(header_value);
            }

            break;
        }

        case s_header_value_lws:
        {
            if (ch == ' ' || ch == '\t')
            {
                state = s_header_value_start;
                CALLBACK_SPACE(header_value);
            }
            else
            {
                state = s_header_field_start;
                goto reexecute_byte;
            }
            break;
        }

        case s_headers_almost_done:
        {
            STRICT_CHECK(ch != LF);

            if (ch != LF) {
                SET_ERRNO(HPE_STRICT);
                goto error;
            }

            if (parser->flags & F_TRAILING) {
                /* End of a chunked request */
                state = s_message_done;
                CALLBACK_NOTIFY_NOADVANCE(chunk_complete);
                goto reexecute_byte;
            }

            state = s_headers_done;

            /* Set this here so that on_headers_complete() callbacks can see it */
            parser->upgrade =
                (parser->flags & F_UPGRADE || parser->method == HTTP_CONNECT);

            /* Here we call the headers_complete callback. This is somewhat
             * different than other callbacks because if the user returns 1, we
             * will interpret that as saying that this message has no body. This
             * is needed for the annoying case of receiving a response to a HEAD
             * request.
             *
             * We'd like to use CALLBACK_NOTIFY_NOADVANCE() here but we cannot, so
             * we have to simulate it by handling a change in errno below.
             */
            size_t header_size = p - data + 1;
            switch (settings->on_headers_complete(parser, nullptr, header_size)) {
            case 0:
                break;

            case 1:
                parser->flags |= F_SKIPBODY;
                break;

            default:
                SET_ERRNO(HPE_CB_headers_complete);
                RETURN(p - data); /* Error */
            }

            if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {
                RETURN(p - data);
            }

            goto reexecute_byte;
        }

        case s_headers_done:
        {
            STRICT_CHECK(ch != LF);

            // we're done parsing headers, reset overflow counters
            parser->nread = 0;
            // (if we now move to s_body_*, then this is irrelevant)
            data_or_header_data_start = p;

            int hasBody = parser->flags & F_CHUNKED || parser->content_length > 0;
            if (parser->upgrade && (parser->method == HTTP_CONNECT ||
                                    (parser->flags & F_SKIPBODY) || !hasBody)) {
                /* Exit, the rest of the message is in a different protocol. */
                state = NEW_MESSAGE();
                CALLBACK_NOTIFY(message_complete);
                RETURN((p - data) + 1);
            }

            if (parser->flags & F_SKIPBODY) {
                state = NEW_MESSAGE();
                CALLBACK_NOTIFY(message_complete);
            } else if (parser->flags & F_CHUNKED) {
                /* chunked encoding - ignore Content-Length header */
                state = s_chunk_size_start;
            } else {
                if (parser->content_length == 0) {
                    /* Content-Length header given but zero: Content-Length: 0\r\n */
                    state = NEW_MESSAGE();
                    CALLBACK_NOTIFY(message_complete);
                } else if (parser->content_length > 0) {
                    /* Content-Length header given and non-zero */
                    state = s_body_identity;
                } else {
                    unsigned short sc = parser->status_code;
                    if (parser->type == HTTP_REQUEST ||
                            ((100 <= sc && sc <= 199) || sc == 204 || sc == 304)) {
                        /* Assume content-length 0 - read the next */
                        state = NEW_MESSAGE();
                        CALLBACK_NOTIFY(message_complete);
                    } else {
                        /* Read body until EOF */
                        state = s_body_identity_eof;
                    }
                }
            }

            break;
        }

        case s_body_identity:
        {
            uint64_t to_read = MIN(parser->content_length, (data + len) - p);

            assert(parser->content_length > 0);

            /* The difference between advancing content_length and p is because
             * the latter will automatically advance on the next loop iteration.
             * Further, if content_length ends up at 0, we want to see the last
             * byte again for our message complete callback.
             */
            MARK(body);
            parser->content_length -= to_read;
            p += to_read - 1;

            if (parser->content_length == 0) {
                state = s_message_done;

                /* Mimic CALLBACK_DATA_NOADVANCE() but with one extra byte.
                 *
                 * The alternative to doing this is to wait for the next byte to
                 * trigger the data callback, just as in every other case. The
                 * problem with this is that this makes it difficult for the test
                 * harness to distinguish between complete-on-EOF and
                 * complete-on-length. It's not clear that this distinction is
                 * important for applications, but let's keep it for now.
                 */
                _CALLBACK_DATA(body, p - body_mark + 1, p - data);
                goto reexecute_byte;
            }

            break;
        }

        /* read until EOF */
        case s_body_identity_eof:
            MARK(body);
            p = data + len - 1;

            break;

        case s_message_done:
            state = NEW_MESSAGE();
            parser->nread = 0;
            data_or_header_data_start = p;
            CALLBACK_NOTIFY(message_complete);
            if (parser->upgrade) {
                /* Exit, the rest of the message is in a different protocol. */
                RETURN((p - data) + 1);
            }
            break;

        case s_chunk_size_start:
        {
            assert(parser->flags & F_CHUNKED);

            unhex_val = unhex[(unsigned char)ch];
            if (unhex_val == -1) {
                SET_ERRNO(HPE_INVALID_CHUNK_SIZE);
                goto error;
            }

            parser->content_length = unhex_val;
            state = s_chunk_size;
            break;
        }

        case s_chunk_size:
        {
            assert(parser->flags & F_CHUNKED);

            if (ch == CR) {
                state = s_chunk_size_almost_done;
                break;
            }

            unhex_val = unhex[(unsigned char)ch];

            if (unhex_val == -1) {
                if (ch == ';' || ch == ' ') {
                    state = s_chunk_parameters;
                    break;
                }

                SET_ERRNO(HPE_INVALID_CHUNK_SIZE);
                goto error;
            }

            if (parser->content_length > (INT64_MAX - unhex_val) >> 4) {
                /* overflow */
                SET_ERRNO(HPE_HUGE_CHUNK_SIZE);
                goto error;
            }
            parser->content_length *= 16;
            parser->content_length += unhex_val;
            break;
        }

        case s_chunk_parameters:
        {
            assert(parser->flags & F_CHUNKED);
            /*
             * just ignore this shit. TODO check for overflow
             * TODO: It would be nice to pass this information to the
             * on_chunk_header callback.
             */
            if (ch == CR) {
                state = s_chunk_size_almost_done;
                break;
            }
            break;
        }

        case s_chunk_size_almost_done:
        {
            assert(parser->flags & F_CHUNKED);
            STRICT_CHECK(ch != LF);

            if (parser->content_length == 0) {
                parser->flags |= F_TRAILING;
                state = s_header_field_start;
                CALLBACK_NOTIFY(chunk_header);
            } else {
                state = s_chunk_data;
                CALLBACK_NOTIFY(chunk_header);
            }
            break;
        }

        case s_chunk_data:
        {
            uint64_t to_read = MIN(parser->content_length, (data + len) - p);

            assert(parser->flags & F_CHUNKED);
            assert(parser->content_length > 0);

            /* See the explanation in s_body_identity for why the content
             * length and data pointers are managed this way.
             */
            MARK(body);
            parser->content_length -= to_read;
            p += to_read - 1;

            if (parser->content_length == 0) {
                state = s_chunk_data_almost_done;
            }

            break;
        }

        case s_chunk_data_almost_done:
            assert(parser->flags & F_CHUNKED);
            assert(parser->content_length == 0);
            STRICT_CHECK(ch != CR);
            state = s_chunk_data_done;
            CALLBACK_DATA(body);
            break;

        case s_chunk_data_done:
            assert(parser->flags & F_CHUNKED);
            STRICT_CHECK(ch != LF);
            state = s_chunk_size_start;
            parser->nread = 0;
            data_or_header_data_start = p;
            CALLBACK_NOTIFY(chunk_complete);
            break;

        default:
            assert(0 && "unhandled state");
            SET_ERRNO(HPE_INVALID_INTERNAL_STATE);
            goto error;
        }
    }

    /* We can check for overflow here because in Proxygen, len <= ~8KB and so the
     * worst thing that can happen is that we catch the overflow at 88KB rather
     * than at 80KB.
     * In case of chunk encoding, we count the overflow for every
     * chunk separately.
     * We zero the nread counter (and reset data_or_header_data_start) when we
     * start parsing a new message or a new chunk.
     */
    if (PARSING_HEADER(state)) {
        parser->nread += p - data_or_header_data_start;
        if (parser->nread > HTTP_MAX_HEADER_SIZE) {
            SET_ERRNO(HPE_HEADER_OVERFLOW);
            goto error;
        }
    }

    /* Run callbacks for any marks that we have leftover after we ran out of
     * bytes. There should be at most one of these set, so it's OK to invoke
     * them in series (unset marks will not result in callbacks).
     *
     * We use the NOADVANCE() variety of callbacks here because 'p' has already
     * overflowed 'data' and this allows us to correct for the off-by-one that
     * we'd otherwise have (since CALLBACK_DATA() is meant to be run with a 'p'
     * value that's in-bounds).
     */

    assert(((header_field_mark ? 1 : 0) +
            (header_value_mark ? 1 : 0) +
            (url_mark ? 1 : 0)  +
            (reason_mark ? 1 : 0)  +
            (body_mark ? 1 : 0)) <= 1);

    CALLBACK_DATA_NOADVANCE(header_field);
    CALLBACK_DATA_NOADVANCE(header_value);
    CALLBACK_DATA_NOADVANCE(url);
    CALLBACK_DATA_NOADVANCE(reason);
    CALLBACK_DATA_NOADVANCE(body);

    RETURN(len);

error:
    if (HTTP_PARSER_ERRNO(parser) == HPE_OK) {
        SET_ERRNO(HPE_UNKNOWN);
    }

    RETURN(p - data);
}


const char * http_method_str (enum http_method m)
{
    return method_strings[m];
}


void
http_parser_init (http_parser *parser, enum http_parser_type t)
{
    parser->type = t;
    parser->state = (t == HTTP_REQUEST ? s_pre_start_req : (t == HTTP_RESPONSE ? s_pre_start_res : s_pre_start_req_or_res));
    parser->nread = 0;
    parser->upgrade = 0;
    parser->flags = 0;
    parser->method = 0;
    parser->http_errno = HPE_OK;
}

const char *
http_errno_name(enum http_errno err) {
    assert(err < (sizeof(http_strerror_tab)/sizeof(http_strerror_tab[0])));
    return http_strerror_tab[err].name;
}

const char *
http_errno_description(enum http_errno err) {
    assert(err < (sizeof(http_strerror_tab)/sizeof(http_strerror_tab[0])));
    return http_strerror_tab[err].description;
}


static enum http_host_state
http_parse_host_char(enum http_host_state s, const char ch) {
    switch(s) {
    case s_http_userinfo:
            case s_http_userinfo_start:
                    if (ch == '@') {
                    return s_http_host_start;
                }

        if (IS_USERINFO_CHAR(ch)) {
            return s_http_userinfo;
        }
        break;

    case s_http_host_start:
        if (ch == '[') {
            return s_http_host_v6_start;
        }

        if (IS_HOST_CHAR(ch)) {
            return s_http_host;
        }

        break;

    case s_http_host:
        if (IS_HOST_CHAR(ch)) {
            return s_http_host;
        }

    /* FALLTHROUGH */
    case s_http_host_v6_end:
        if (ch == ':') {
            return s_http_host_port_start;
        }

        break;

    case s_http_host_v6:
        if (ch == ']') {
            return s_http_host_v6_end;
        }

    /* FALLTHROUGH */
    case s_http_host_v6_start:
        if (IS_HEX(ch) || ch == ':' || ch == '.') {
            return s_http_host_v6;
        }

        break;

    case s_http_host_port:
    case s_http_host_port_start:
        if (IS_NUM(ch)) {
            return s_http_host_port;
        }

        break;

    default:
        break;
    }
    return s_http_host_dead;
}

static int
http_parse_host(const char * buf, struct http_parser_url *u, int found_at) {
    enum http_host_state s;

    const char *p;
    size_t buflen = u->field_data[UF_HOST].off + u->field_data[UF_HOST].len;

    u->field_data[UF_HOST].len = 0;

    s = found_at ? s_http_userinfo_start : s_http_host_start;

    for (p = buf + u->field_data[UF_HOST].off; p < buf + buflen; p++) {
        enum http_host_state new_s = http_parse_host_char(s, *p);

        if (new_s == s_http_host_dead) {
            return 1;
        }

        switch(new_s) {
        case s_http_host:
            if (s != s_http_host) {
                u->field_data[UF_HOST].off = p - buf;
            }
            u->field_data[UF_HOST].len++;
            break;

        case s_http_host_v6:
            if (s != s_http_host_v6) {
                u->field_data[UF_HOST].off = p - buf;
            }
            u->field_data[UF_HOST].len++;
            break;

        case s_http_host_port:
            if (s != s_http_host_port) {
                u->field_data[UF_PORT].off = p - buf;
                u->field_data[UF_PORT].len = 0;
                u->field_set |= (1 << UF_PORT);
            }
            u->field_data[UF_PORT].len++;
            break;

        case s_http_userinfo:
            if (s != s_http_userinfo) {
                u->field_data[UF_USERINFO].off = p - buf ;
                u->field_data[UF_USERINFO].len = 0;
                u->field_set |= (1 << UF_USERINFO);
            }
            u->field_data[UF_USERINFO].len++;
            break;

        default:
            break;
        }
        s = new_s;
    }

    /* Make sure we don't end somewhere unexpected */
    switch (s) {
    case s_http_host_start:
    case s_http_host_v6_start:
    case s_http_host_v6:
    case s_http_host_port_start:
    case s_http_userinfo:
    case s_http_userinfo_start:
        return 1;
    default:
        break;
    }

    return 0;
}


int
http_parser_parse_url(const char *buf, size_t buflen, int is_connect,
                      struct http_parser_url *u)
{
    enum state s;
    const char *p;
    enum http_parser_url_fields uf, old_uf;
    int found_at = 0;

    u->port = u->field_set = 0;
    s = is_connect ? s_req_server_start : s_req_spaces_before_url;
    uf = old_uf = UF_MAX;

    for (p = buf; p < buf + buflen; p++) {
        s = parse_url_char(s, *p);

        /* Figure out the next field that we're operating on */
        switch (s) {
        case s_dead:
            return 1;

        /* Skip delimeters */
        case s_req_schema_slash:
        case s_req_schema_slash_slash:
        case s_req_server_start:
        case s_req_query_string_start:
        case s_req_fragment_start:
            continue;

        case s_req_schema:
            uf = UF_SCHEMA;
            break;

        case s_req_server_with_at:
            found_at = 1;

        /* FALLTROUGH */
        case s_req_server:
            uf = UF_HOST;
            break;

        case s_req_path:
            uf = UF_PATH;
            break;

        case s_req_query_string:
            uf = UF_QUERY;
            break;

        case s_req_fragment:
            uf = UF_FRAGMENT;
            break;

        default:
            assert(!"Unexpected state");
            return 1;
        }

        /* Nothing's changed; soldier on */
        if (uf == old_uf) {
            u->field_data[uf].len++;
            continue;
        }

        u->field_data[uf].off = p - buf;
        u->field_data[uf].len = 1;

        u->field_set |= (1 << uf);
        old_uf = uf;
    }

    /* host must be present if there is a schema */
    /* parsing http:///toto will fail */
    if ((u->field_set & ((1 << UF_SCHEMA) | (1 << UF_HOST))) != 0) {
        if (http_parse_host(buf, u, found_at) != 0) {
            return 1;
        }
    }

    /* CONNECT requests can only contain "hostname:port" */
    if (is_connect && u->field_set != ((1 << UF_HOST)|(1 << UF_PORT))) {
        return 1;
    }

    if (u->field_set & (1 << UF_PORT)) {
        /* Don't bother with endp; we've already validated the string */
        unsigned long v = strtoul(buf + u->field_data[UF_PORT].off, nullptr, 10);

        /* Ports have a max value of 2^16 */
        if (v > 0xffff) {
            return 1;
        }

        u->port = (uint16_t) v;
    }

    return 0;
}

void
http_parser_pause(http_parser *parser, int paused) {
    /* Users should only be pausing/unpausing a parser that is not in an error
     * state. In non-debug builds, there's not much that we can do about this
     * other than ignore it.
     */
    if (HTTP_PARSER_ERRNO(parser) == HPE_OK ||
            HTTP_PARSER_ERRNO(parser) == HPE_PAUSED) {
        SET_ERRNO((paused) ? HPE_PAUSED : HPE_OK);
    } else {
        assert(0 && "Attempting to pause parser in error state");
    }
}

#if __cplusplus
}
#endif /* __cplusplus */
